linux-kernel - Re: [PATCH] kvm: fix waitqueue_active without memory barrier in virt/kvm/async

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Message-ID: <17EC94B0A072C34B8DCF0D30AD16044A02874DAA@BPXM09GP.gisp.nec.co.jp>
Date:	Fri, 9 Oct 2015 12:21:37 +0000
From:	Kosuke Tatsukawa <tatsu@...jp.nec.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
CC:	Gleb Natapov <gleb@...nel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kvm: fix waitqueue_active without memory barrier in
 virt/kvm/async_pf.c 

Paolo Bonzini wrote:
> On 09/10/2015 11:04, Kosuke Tatsukawa wrote:
>> smp_store_mb() called from set_current_state(), which is called from
>> prepare_to_wait() should prevent reordering such as below from
>> happening.  wait_event*() also calls set_current_state() inside.
>
> Ah, I missed that set_current_state has a memory barrier in it.  The
> patch is okay, but please expand the comment to say that this memory
> barrier pairs with prepare_to_wait's set_current_state().

thank you for the comment.  I'll send a new version of the patch with
the modification.
---
Kosuke TATSUKAWA  | 3rd IT Platform Department
                  | IT Platform Division, NEC Corporation
                  | tatsu@...jp.nec.com
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